Aviva Premiership league leaders Saracens will be out to maintain their recent good form when they take on Ulster in the Heineken Cup quarter-finals and reach the last four for the first time since 2008.

The north London side have been in red-hot form since they moved into their new home at Allianz Park. They have won all three of their matches that they have hosted there, as well as win tricky assignments away to Leicester Tigers and London Wasps that continued an unbeaten run in the league that stretches back to November.

Brad Barritt, David Strettle, Schalk Brits, Matt Stevens, Alistair Hargreaves and Kelly Brown are all back in the team for the match at Twickenham on Saturday after missing the win over Wasps.

Ulster are eager to repeat their run to last year's final and they include wing Tommy Bowe in the squad for the first time since December when suffered knee ligament damage. With Ruan Pienaar pulling the strings from scrum-half, John Smit, his one-time team-mate for the Sharks and South Africa, is well aware of the threat that Saracens will face.

"I think they've built a good team over the last few years," Smit said. "They have similar structures and similar methods in how they approach competitions, they have a quite a deep squad and they have had guys returning from injury and international commitments.

"Physically they are very difficult to approach from a set-piece point of view; their set-piece is very strong and provides them with a solid base off which to play, and with a game breaker like Pienaar at scrum half they are a very dangerous opposition."

Leicester Tigers meanwhile travel to the south of France to meet Toulon at the Stade Felix Mayol with their eyes set on a first semi-final appearance since 2009, a year in which they lost to Leinster in the final.

It is now over 10 years since the most successful club in English professional rugby won the second of their two consecutive Cup wins and they have named the same team that defeated Northampton Saints 36-8 in their most recent match.

Toulon will be no pushovers though and have led the Top 14 for much of the season. Furthermore with a team filled with England internationals such as Jonny Wilkinson, Andrew Sheridan, Nick Kennedy and the Armitage brothers, Delon and Steffon, Leicester are unlikely to hold too many surprises.

"I'm really looking forward to the challenge," scrum-half Ben Youngs said. "If you look at their team you'd think you're playing the Barbarians, rather than Toulon. I think for us it is the first time we've gone into the game as underdogs, which is great situation to be in; no-one is expecting us to win and we can go there and just take it to them. It is a one-off game and there is a huge amount of pressure on them."

English champions Harlequins will try to put a poor run in the league behind them when they meet 2006 and 2008 champions Munster at the Twickenham Stoop on Sunday.

While a team predominantly made up of their reserves won the LV= Anglo-Welsh Cup three weeks ago, since then they have appeared fatigued during losses to Saracens and Gloucester. With over a week's rest since the loss at Kingsholm and the return of captain Chris Robshaw, the hope is that they will be back to their best against a Munster side that has won only one of their five last fixtures, but who welcome back wing Simon Zebo from injury.

"You can look at the form in different competitions, but this is the Heineken Cup, this is knock-out rugby and this is Munster playing a quarter-final at The Stoop, so we're looking forward to the challenge because it's going to be a tough game to play in," second-row George Robson said.

"It's the third time we've made it to this stage of the Heineken Cup and we're playing against a side who have put the marker down and have made the Heineken Cup what it is with what they've achieved through the years. Anyone who reads anything into their results in the league is missing a trick with what the Heineken Cup means to the province, it's what they live for."

The fourth quarter-final is an-all French affair as Clermont Auvergne welcome Montpellier to their Stade Marcel Michelin fortress. Vern Cotter's team were impressive in the last eight a year ago as they beat Saracens at Vicarage Road, but they lost form and were knocked out by eventual winners Leinster in the last four.

Ludovic Radosavljevic will continue at fly-half in place of Brock James who is out with a torn thigh muscle. Lee Byrne and Sitiveni Sivivatu are back at fullback and wing respectively, while former France international Julien Bonnaire lines up at No.8.

For Montpellier Francois Trinh Duc starts at fly-half, while his fellow French international Fulgence Ouedraogo packs down on the flank. There is no place in the starting side for Scottish international Johnnie Beattie though. He must make do with a place on the bench with Alex Tulou starting at No.8.

Clermont beat Montpellier 36-18 when the sides met in January, but the south coast team won 13-8 at home early in the season and Clermont know they will need to be at their best to preserve their 57-match unbeaten home record.

"We know them very well and it will be like two brothers who fight together all the time," Cotter said. "We know the strengths and weaknesses of Montpellier and they know ours. It will be a winner-takes-all showdown and this will make the game more difficult and intense.

"There is no guarantee that we'll reach the semi-finals. Montpellier has the players to put us in trouble and, like us; they will have every intention of continuing their run."